The menstrual cycle occurs roughly every 28 days after puberty, when an ovum is released from the ovaries and travels to the uterus, where it may be fertilized by a sperm if encountered. If fertilization does not occur, the ovum and some blood and tissue are shed from the uterus in a process called menstruation. Genes from both the mother's ovum and father's sperm combine at fertilization to determine the characteristics inherited from each parent.

1. MENSTRUAL CYCLE AND GENES

2. MENSTRUAL CYCLE
After puberty in girls, ovaries
start to release ova.
One ovum is released about
every 28 days.

3. What is ovulation?
It is a process where an ovum (egg)
travels from the ovaries to the uterus.
Two things can happen:
●
If the ovum finds a sperm, fertilization
takes place and a new baby grows.
●
If the ovum does not find a sperm,
menstruation takes place and the
ovum is released.

4. How does ovulation take place?
The walls of the uterus
have extra blood and
tissue. The egg (ovum) is
ready for fertilization.
If fertilization does not
happen, the ovum dries
up and leave the body
through the vagina.
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5. When does menstruation occur?
Menstruation occurs when
the dried ovum, extra
tissue and some blood
leave the girl’s body once
a month.
Menstruation
Blood and extra tissue

6. Menopause
When women are from 40 to
50, they go through a
process called menopause.
When this happens, women
stop releasing ova.

7. When girls are born, they
have all the ova (eggs) they
will need for the rest of their
lives.

8. GENES
In the nucleus of the ovum,
there are recorded
characteristics from the
mother.
In the nucleus of the sperm,
there are recorded
characteristics from the
father.

9. When the sperm joins an ovum, the
information from the father and the
information from the father combines.

10. That is why we have characteristics from our
mothers and characteristics from our fathers.